Trouble with -5v on Surf PI

[antalaz]

Hi everyone,

during my last session, i got trouble with surf PI.

When i got the coil plugged, i can hear the speaker at a frequency around 1Hz.

When i unplug the coil everything is fine.

i've checked the signals, the parasitic signals seems to come from -5v: it looks like a step function (maybe a capacitor making an oscillation on -5v).

I've tried another coil -> same problem
Replaced pre-amp -> same problem
Replaced 4093 -> same problem
555 doesn't have any parasitic signal on output
Replaced MOSFET -> same problem

I'm still working on it

Any ideas ?

Thanks in advance

[antalaz]

Here is a picture of the output of integrator 0.5V/div 0.2S/div


please help

[waltr]

What about picture of the -5V? Isn't that the problem (based on the thread title)?
Look at output of -5V reg (U6 pin 5 the ICL7660) and on the -5V input pin of the op-amps.
If the -5V input opamps is bad you will not fix this be swapping coils or opamps.
Is the +5V clean?

Please do try to get pics in better focus.

[kt315]

555 doesn't have any parasitic signal on output
---
sorry but original surf using TLC555 chip. open datasheet and you will see - thats CMOS chip,
NOT ORDINARY SILICIUM like NE555 you use.

you can NOT DIRECTLY set NE555 instead TLC555.

[antalaz]

I confirm that i have a TLC555.
I don't have a good camera sorry for quality.

Problem solved: it was the LM chip.

discovered by de-solder the capacitor at the output of integrator (to seperate the audio from the signal processing).

So if you hear one BEEP per second you know where to search

regards